OK, I can see a few things right away.
the "or" construct is expecting to compare two expressions that RESULT in true
or false.
So, the "or 511" is meaningless, or at least not what you're looking for.
Next, I wouldn't recommend "selecting" each cell. It causes WAY too much screen
updating.
What I would do is utilize the Value property as in c.Value
then, the Left function is going to return a character string, but you're
comparing it to a
numeric value, which can be unpredictable.
What you have to do is write  it like:
If ((Left(c.Value, 2) = "50") _
Or (Left(c.Value,2) = "511") _
Or (Left(c.Value,2) = "512") _
Or (Left(c.Value,2) = "531")) Then
I haven't had time to test  it, I'm kind-of in a rush...
hope this helps.